Study shows acid rain improvement

Problems have been caused by nitrogen emissions

Pollution linked to shipping has cast a cloud over new research showing an improvement in levels of acid rain falling on the UK.

The findings of a two-year study into the effect of pollution on the British environment were published on Monday.

The acid sensitive areas are the places which are recovering slowest

Prof David Fowler

Researchers found that the deposits from acid rain had halved in the UK over the last two decades. Acid falling from the atmosphere causes widespread damage, harming the health of fish, animals and humans and even eating away at the brickwork of buildings.

The National Expert Group on Transboundary Air Pollution (Negtap) study identified the largest reductions in the South East and the English East Midlands.

However, the group's chairman, Professor David Fowler, of the Centre for Ecology and Hydrology in Penicuik, Midlothian, said that the west coast of Britain had seen less of an improvement.

"This is a bit of a blow because acid rain has its biggest effect on the west coast of Britain," he told BBC News Online Scotland. "The acid-sensitive areas are the places which are recovering slowest."

Shipping controls

He said that parts of western Scotland and Wales were being hit hardest because of sulphur produced by shipping, along with the effect of emissions from North America.

International agreements have led to large reductions in sulphur and nitrogen emissions in Britain and other EU countries - but these steps do not cover shipping emissions.

The report examined the effect on the environment

Professor Fowler said that shipping tended to use high-sulphur fuels, creating pollution which then came down on European countries.

"The only way we can control that is by expanding the controls to shipping," he said. He added that the amount of pollution crossing the Atlantic from America and Canada was not known.

The aim of the Negtap study, which was sponsored by Department for Environment, Food and Rural Affairs (Defra), was to determine the effect of the action taken over the last two decades to reduce pollution.

'Very slow'

The researchers predicted that the number of UK ecosystems where acidification was above critical levels would decline from 71% to 47% by 2010.

Professor Fowler said: "There is good news. Things are getting better.

"We can see clear evidence of chemical change which is consistent with recovery. The down side is that the recovery process is very slow - it takes decades and some areas may never recover."

The research also found that the concentrations of ozone at ground level during peak periods, like summer smog, had declined by 30% over the last 20 years due to a fall in emissions.

But the background concentrations are on the rise - and are expected to exceed the levels known to be damaging to plant life during this century.

However, Professor Fowler admitted that it was not yet known what the effect of this would be on vegetation in areas like the Scottish Borders.

Creeping up

"Throughout the Northern Hemisphere emissions are going up, so the background is gradually creeping up," he said.

Acid rain

Oxides of sulphur and nitrogen are thrown into the atmosphere from the burning of fossil fuels, such as coal, gas, and oil

These oxides combine with water to form dilute sulphuric and nitric acid, and other pollutants

The greatest concern now centres on the effect on the country's ecosystems of nitrogen produced by traffic and industry and ammonia from intensive farming.

In examining the effect of eutrophication, a large change has been detected towards those species that grow very rapidly when exposed to nitrogen.

Professor Fowler said a number of "hot-spots" had been identified close to motorways, industries and extensive farming operations.

"The actions taken politically to reduce that have not produced much of a change. That continues to be a problem," he said.

Professor Fowler said that the obvious move to limit the damage being caused by nitrogen and ammonia was to reduce the level of emissions, for example in areas close to nature reserves.